Croaker Climate

The fish's future is bright, collaborative study suggests

Barb DeLuisi, Spring 2010

Jonathan Hare of NOAA's Northeast Fisheries Science Center in Narragansett,
R.I. wanted to know how climate change information could be used to help
plan for the future of our fisheries. "Most current management plans do not
include the effect of climate change on specific fish populations, some of
which will increase and others decrease as a result," said Hare.

Hare knew that the Atlantic croaker would be an excellent species of fish
for such a study since its survival is directly related to temperature
changes. Millions of pounds of this mild-flavored fish are caught in the
United States every year. In the winter, croakers travel to shallow bay
areas along the U.S. northeast coast and lay eggs. Once hatched, the young
fish have a better chance of making it to adulthood when winters are warm.
To figure out how climate change might affect croakers, Hare needed the
right kind of climate information.

So Hare gave Mike Alexander, of PSD, a
call. The two had previously served together on a scientific committee, and
Hare knew Alexander worked with climate data.

"I was excited about the prospect of collaborating," said Alexander, a
climate scientist who has always been interested in marine biology. He had
already done research on how climate variability may impact amphibians and
stellar sea lions, for example. He worked with Hare to determine what data
would be best for this study and where to get it.

Because ocean temperatures in near-shore bays and estuaries generally track
the overlying air temperature, the latter could be used as input to the
croaker model. Alexander and Jamie Scott (PSD and CIRES),
extracted air temperatures along the U.S. East Coast spanning 1870-2001 from 14 General
Circulation Models (GCMs) that were used in the Intergovernmental Panel on
Climate Change Fourth Assessment Report. Also used from this widely
established and freely available dataset were three different CO2 scenarios
that estimate greenhouse gas and air temperature changes from the present
out to the year 2100. Alexander also helped explain the climate models, how
to use the data, and checked the consistency of the information both in
nature and within the model.

Hare and his colleagues at NFSC then fed the climate data into a fish
population model that combined temperature and fishing rates; two key
factors that affect fish mortality. This new fish-climate model is one of
the first to look at the relationship between temperature change and its
impact on a specific fish population.

The results looked pretty positive for the Atlantic croaker: If global
temperatures continue to increase as predicted, more croakers will make it
to adulthood and, therefore, the population will grow. Climate change may
also widen the geographic range of croakers. Currently the Chesapeake Bay
houses the highest density of croakers. Over time their range could expand
into an area around New York.

The team of scientists published their work in the March 2010 issue of
Ecology Applications.

Alexander cautioned that the results are specific to the Atlantic croaker:
"While climate change may increase the population and range of croakers, it
is likely to adversely affect other fish such as cod," he said. Because
climate change information has not traditionally been included in fisheries
planning, this model could be a breakthrough in performing stock
assessments and planning for sustainable fisheries.

Hare concluded: "Our results demonstrate that climate effects on fisheries
must be identified, understood, and incorporated into the scientific advice
provided to managers if sustainable exploitation is to be achieved and
maintained in a changing climate."

Current GCMs can only provide forecasts out to 50-100 years, a bit far in
the future for most fisheries planning, said Hare. Shorter-term forecasts
ranging between 5-50 years may soon become available for incorporation into
fisheries models, to make even better informed decisions.